Unit for delivering fuel from the fuel tank to the internal combustion engine of a motor vehicle

ABSTRACT

A unit for delivery of fuel from the fuel tank to the internal combustion engine of a motor vehicle includes a feed pump which is arranged in the fuel tank and constructed as a flow pump with substantially circular-cylindrical impeller driven in rotation in a correspondingly circular-cylindrical pump chamber. In at least one of the two chamber end walls, at least one approximately annular delivery duct which is groove-like in cross section extends from a suction opening which opens into the pump chamber to a pressure opening leading out of the latter. This end wall of the chamber is penetrated in the region of the pressure opening by a bore hole connecting the pump chamber with a region of the system in which low pressure prevails. Gas bubbles can be removed from the pump and accordingly from the delivery path in a particularly reliable and simple manner in that this bore hole is situated in a sealing surface which defines the delivery duct in the radial direction with reference to the axis of rotation of the impeller.

BACKGROUND OF THE INVENTION

The present invention relates to a unit for delivering fuel from a fueltank to the internal combustion engine of a motor vehicle.

More particularly, it relates to a unit of the above mentioned generaltype which has a feed pump arranged in a fuel tank and constructed as aflow pump with a substantially circular-cylindrical impeller rotating ina circular-cylindrical pump chamber.

Units of the above mentioned general type are known in the art. A feedunit is already known (DE-OS 35 09 374) in which this bore hole isarranged directly in the delivery duct and provided with a resilientvalve flap which remains in its open position while gas is beingconveyed, but when fuel is delivered is deformed against spring force bythe more "viscous" medium and closes the opening of the bore hole on theduct side. However, such a construction requires a particularly costlyassembly of the valve flap. There is also the risk that the open valveflap will scrape against the impeller of the feed pump when gas isconveyed causing unwanted noise and will finally be destroyed.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a unitfor delivering fuel from a fuel tank to an internal combustion engine,which avoids the disadvantages of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a unit in which an end wall of the pump chamber is penetratedin the region of a pressure opening by a bore hole which connects thepump chamber with a region of the system with a low pressure, and thebore hole in accordance with the present invention is located in asealing surface which defines a delivery duct in a radial direction withreference to an axis of rotation of the impeller.

When the unit is designed in accordance with the present invention, ithas the advantage over the prior art that there are no movablestructural members which are subject to wear during operation. It isalso unnecessary to assemble such parts.

In a particularly advantageous construction of the feed unit, the bladeedge has a first and second ring of blades, the second blade ring havinga greater radius than the first blade ring, and two delivery ductsassociated with the respective blade ring are located in the end wall ofthe chamber. The inner delivery duct is connected with the outerdelivery duct via an intermediate duct. The suction opening is arrangedat the inner delivery duct, while the pressure opening is arranged atthe outer delivery duct. The bore hole is located in a region of thesealing surface which extends at least substantially between the twodelivery ducts.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of an arrangement with a fuel supply tank,a fuel feed unit, and an internal combustion engine of a motor vehicle;

FIG. 2 is an enlarged view of a partial longitudinal section through thefeed unit according to FIG. 1 along line II--II in FIG. 3, and

FIG. 3 shows a section through a pump chamber cover on the suctionopening side belonging to the feed unit according to FIG. 2 along lineIII--III.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows a fuel tank 10 in which a fuel feed unit 12 is arranged. Apressure line 16 leading to an internal combustion engine 18 isconnected to a pressure sleeve 14 of the fuel feed unit 12. Duringoperation of the internal combustion engine 18, the fuel feed unit 12sucks fuel out of the fuel tank 10 via a suction sleeve 13 and deliversthe fuel to the internal combustion engine 18. The fuel feed unit 12 isoutfitted with an electric drive motor 20 (FIG. 2) whose motor armature22 sits on an armature shaft 24. One end 26 of the armature shaft 24penetrates a dividing wall 28 which divides a space 30 containing theelectric motor 20 from a feed pump 32. The feed pump 32 is constructedas a stream or flow pump. Its impeller 34 is connected with the end 26of the armature shaft 24 so as to be fixed with respect to rotationrelative to it. The impeller 34 is arranged in a pump chamber 36 whichis defined toward the drive motor 20 by the dividing wall 28 on one sideand on the other side by a cover 38 in which the suction sleeve 13 islocated. In the embodiment example the feed pump is constructed as atwo-stage flow pump. However, this has no importance with respect to thepresent invention since the invention can also easily be applied in asingle-stage flow pump. The impeller 34 which has an inner, first ring40 of blades rotates in the pump chamber 36. The impeller 34 has asecond ring 42 of blades in its peripheral area. The second ring 42includes two partial rings, each of which is constructed on one of thetwo end faces 44, 46 of the impeller 34 which has a substantiallycircular-cylindrical shape. The two partial blade rings of the secondblade ring 42 are provided with reference numbers 51 and 53 in FIG. 2.The dividing wall 28 is securely connected with a housing part 54enclosing the feed unit 12. The pump chamber 36 is closed by the cover38 on the side of the impeller 34 remote of the dividing wall 28. Thiscover 38 is held in its receptacle by an inwardly shaped edge 56 of thehousing part 54. As shown in FIG. 3, a first or inner delivery duct 50extends in the counterclockwise direction from a suction opening 58located in the suction sleeve 13 to an intermediate duct 60 extending ina substantially radial direction. A second or outer delivery duct 52 isconnected to the intermediate duct 60. This delivery duct 52 extendsalong an edge shoulder 62 of the cover 38 into the vicinity of theintermediate duct 60. Corresponding delivery ducts 50, 52 are alsoarranged in the dividing wall 28. As seen in the radial direction, thetwo delivery ducts 50 and 52 are situated at a distance from one anotherso that a dividing surface 64 remains between them. Since the twodelivery ducts 50 and the two delivery ducts 52 are situated oppositeeach other as seen in the axial direction, the dividing surfaces 64 ofthe dividing wall 28 and of the cover 38 are also situated opposite eachother. In the terminating region 66 of the delivery duct 52 in thecover, 38 a pressure opening 68 is situated opposite the latter in thedividing wall 28 and connects the delivery duct 52 with the space 30which, as shown in FIG. 1, contains the pressure sleeve 14. FIG. 3further shows that three bore holes 70 are arranged in the dividingsurface 64 of the cover 48 and lead from the pump chamber 36 to thesuction side of the pump 32. These bore holes 70 thus connect the pumpchamber with a region of the system in which low pressure prevails. Inthe embodiment example this region is the interior of the tank. Thesethree gas-discharge bore holes 70 are arranged one after the other, asseen in the rotating direction (arrow 72) of the rotor 34, in atrough-like groove 74 extending in the rotating direction shown by thearrow 72 between the two delivery ducts 50 and 52. The two deliveryducts 50 and 52 thus extend from the suction opening 58 to the pressureopening 68. The cover 38 contains the suction opening 58 and thedividing wall 28 contains the pressure opening 68. The hydraulicconnection between the identical delivery ducts situated opposite oneanother in the axial direction is effected by the openings between theblades of the first ring 40 and by an annular gap 76 remaining betweenthe edge shoulder 62 and the outer surface area of the impeller 34. Withthe understanding that the invention can also be realized with only onebore hole 70 and that this single bore hole is the central bore holeshown in FIG. 3, the configuration of the trough-like groove 74 can alsobecome apparent in that a portion of the groove 74 extends in thecircumferential direction (arrow 72) and another portion of the groove74 extends opposite this circumferential direction of the impeller 34.The two walls 28 and 38 defining the pump chamber 36 in the axialdirection of the rotor 34 are produced from plastic in the embodimentexample. The trough-like groove 74 is molded into the cover 38.

The feed unit according to the invention operates in the followingmanner:

When the impeller 34 is driven by the electric motor 20 the feed pump 32sucks fuel out of the fuel tank 10 via the suction opening 58 andpresses it in the direction of arrow 72 through the first delivery duct50 and through the intermediate duct 60 into the outer delivery duct 52,from which the fuel enters the space 30 of the drive motor 20 via thepressure opening 68 and exits via the pressure sleeve 14. There areslight radial gaps between the two end faces of the impeller 34 and thewalls 38, 28 facing the latter. Gas bubbles present in the delivery duct50, 60, 52 are pressed out of the delivery ducts in the direction of thearrow 78 via these radial gaps and are received by the trough-likegroove 74. From there, the gas bubbles leave the pump chamber 36 via thebore holes 70. The gas bubbles in question are formed, for instance, bycavitation occurring in certain regions of the feed pump. Such gasbubbles can also occur if the pump has been completely empty and thefeed pump first delivers this air. In any event, gas bubbles must beprevented from remaining in the system, reaching the internal combustionengine 18 via the pressure line 16 and disturbing operation of thelatter.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in aunit for delivering fuel from the fuel tank to the internal combustionengine of a motor vehicle, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. A unit for delivering fuel from afuel tank to an internal combustion engine of a motor vehicle,comprising a flow pump having a plurality of walls forming a pumpchamber and including two end walls in at least one of which end walls adelivery duct is formed, said at least one end wall having a bore holewhich connects said pump chamber with a low pressure region, said pumpfurther having an impeller which rotates in said pump chamber about anaxis of rotation; means forming a suction opening which opens into saidpump chamber and from which said delivery duct extends, and a pressureopening leading out of said pump chamber, said one end wall having asealing surface which defines inner and outer limits of said deliveryduct in a radial direction with respect to said axis of rotation of saidimpeller, said bore hole being located in said sealing surface, saidsealing surface having a trough-like groove proceeding from said borehole and having one groove part extending in a rotation direction andanother part extending opposite to the rotation direction of saidimpeller.
 2. A unit as defined in claim 1, wherein said impeller issubstantially circular-cylindrical, said pump chamber beingcorrespondingly circular-cylindrical, said delivery duct being annular.3. A unit as defined in claim 1, wherein said trough-like groove hasadditional bore holes.
 4. A unit as defined in claim 1, wherein saidimpeller has a first blade ring and a second blade ring formed so thatsaid second blade ring has a greater radius than said first blade ring,said at least one end wall of said chamber having another delivery duct,said delivery ducts being associated with said blade rings and includingan inner delivery duct and an outer delivery duct connected with oneanother via an intermediate duct, said suction opening being arranged atsaid inner delivery duct, while said pressure opening is arranged atsaid outer delivery duct, said sealing surface in which said bore holeis located extending at least substantially between said two deliveryducts.
 5. A unit as defined in claim 9, wherein said impeller has afirst blade ring and a second blade ring formed so that said secondblade ring has a greater radius than said first blade ring, said atleast one end wall of said chamber having another delivery duct, saiddelivery ducts being associated with said blade rings and including aninner delivery duct and an outer delivery duct connected with oneanother via n intermediate duct, said suction opening being arranged atsaid inner delivery duct, while said pressure opening is arranged atsaid outer delivery duct, said sealing surface in which said bore holeis located extending at least substantially between said two deliveryducts, said trough-like duct extending in a radial direction betweensaid two delivery ducts until a region of said intermediate duct.
 6. Aunit as defined in claim 1, wherein said at least one wall of saidchamber is formed as a cover composed of a plastic material.
 7. A unitas defined in claim 1, wherein said at least one wall of said chamber iscomposed of an injection molded plastic material.
 8. A unit as definedin claim 9, wherein said at least one end wall is formed as a cover inwhich said trough-like groove is formed.
 9. A unit as defined in claim1; and further comprising a fuel tank from which said feed pump deliversfuel, said fuel tank enclosing a space, said pump chamber having aregion of higher pressure which is connected by said bore hole withspace of said fuel tank.